本文的truncate恢复只针对于堆表(非lob)进行了测试，其实对于分区表和lob段的恢复原理是一样的。

根据之前对truncate原理的分析，truncate是不能通过闪回查询或者logminer的方式来恢复的，因为truncate操作不会对数据块进行任何操作。那么truncate应该如何恢复呢？下面列出几种常见的方法可供参考。

• 数据库闪回(要求flashback database开启，并且必要的闪回日志和归档日不能丢失，因为闪回数据库不仅仅需要应用闪回日志，归档日志也是需要的。)
• 异机恢复(要求有可用的备份以及必要的归档日志)
• TSPITR(要求有可用的备份以及必要的归档日志）

其中数据库闪回和TSPITR对数据库影响较大。

假如数据库flashback database没有开启，并且无备份的情况下该如何恢复呢？

本文介绍两种不常见的方法，重点介绍第二种修复元数据方式：

• ODU(要求数据不被覆盖，如果数据被覆盖也可以最大程度的恢复数据)
• 通过修复元数据来实现恢复truncate(要求有truncate操作时的redo信息，并且数据不被覆盖，如果数据被覆盖也可以最大程度的恢复数据)

01

ODU的方式

ODU是前Oracle ACED 熊军开发的一款专业而且强大的Oracle恢复工具，适用于所有场景下的恢复，具体查看http://www.oracleodu.com/cn/，这里简单介绍一下ODU恢复truncate的原理。

ODU恢复truncate的原理是通过scan数据文件生成一个ext.odu的文件，该文件是按照表的dataobj#扫描出具体的extent信息，然后通过ext.odu可以导出需要恢复的表的数据，最终再导入到数据库中。

02

修复元数据的方式

根据之前对truncate原理的分析，truncate的实质是在不修改数据块的情况下，通过修改segment header的data_object_id,hwm,extent map，aux map等信息来实现清空表的目的，其中还涉及数据字典基表以及L1、L2位图块的修改，那么对于通过修改元数据的方式去恢复，首先需要确认哪些元数据块和数据字典是需要恢复的。

通过10046的跟踪发现(可以去验证一下，需要flush shared pool和buffer cache)，全表扫描查询或者是通过rowid去查询一定会访问segment header，但是不会去访问任何L1、L2位图块的，访问的数据字典基表包括user$、obj$、tab$、tab_stats$、ts$、seg$、ind$、ind_stats$、col$、objauth$、cdef$、histgrm$、hist_head$，这里重点关注之前通过10046跟踪truncate操作有更改的基表obj$、tab$、seg$、tab_stats$(统计信息不用管)，其中seg$经过测试只要block#、file#、ts#不被更改就无需理会，而truncate操作是不会修改seg$的ts#、file#、block#的，具体测试过程如下：

SYS@TEST(test):1>select obj#,dataobj# from obj$ where owner# in (select user# from user$ where name='TEST') and name='T1';
      OBJ#   DATAOBJ#
---------- ----------
     17284      17284


SYS@TEST(test):1>select TS#,FILE#,BLOCK# from tab$ where OBJ#=17284;
 
       TS#      FILE#     BLOCK#
---------- ---------- ----------
         9          4        290
                
SYS@TEST(test):1>update seg$ set blocks=1,extents=1,minexts=1,maxexts=1,extsize=1,bitmapranges=1,hwmincr=1,type#=1 where ts#=9 and file#=4 and block#=290;
 
1 row updated.
 
SYS@TEST(test):1>commit;
 
Commit complete.
 
SYS@TEST(test):1>alter system flush shared_pool;
 
System altered.
 
SYS@TEST(test):1>select count(*) from test.t1;
 
  COUNT(*)
----------
     14164
        
SYS@TEST(test):1>delete from seg$ where ts#=9 and file#=4 and block#=290;
 
1 row deleted.
 
SYS@TEST(test):1>commit;


Commit complete.
 
SYS@TEST(test):1>select count(*) from test.t1;
select count(*) from test.t1
                          *
ERROR at line 1:
ORA-00600: internal error code, arguments: [ktsircinfo_num1], [9], [4], [290], [], [], [], [], [], [], [], []

所以需要恢复的元数据块和数据字典基表以及内容为：

• segment header(dataobj#、LHWM、HHWM、extent map、aux map以及extents个数)
• tab$(dataobj#)
• obj$(dataobj#)

下面提供segment header的信息对应的offset：

segment header dump：

Extent Control Header
  -----------------------------------------------------------------
  Extent Header:: spare1: 0      spare2: 0      #extents: 28     #blocks: 1664  
                  last map  0x00000000  #maps: 0      offset: 2716  
      Highwater::  0x01405b83  ext#: 27     blk#: 3      ext size: 128  
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 1539  
  mapblk  0x00000000  offset: 27    
                   Unlocked
  --------------------------------------------------------
  Low HighWater Mark :
      Highwater::  0x01405b83  ext#: 27     blk#: 3      ext size: 128  
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 1539  
  mapblk  0x00000000  offset: 27    
  Level 1 BMB for High HWM block: 0x01405b80
  Level 1 BMB for Low HWM block: 0x01405b80
  --------------------------------------------------------
  Segment Type: 1 nl2: 1      blksz: 8192   fbsz: 0      
  L2 Array start offset:  0x00001434
  First Level 3 BMB:  0x00000000
  L2 Hint for inserts:  0x01400769
  Last Level 1 BMB:  0x01405b81
  Last Level II BMB:  0x01400769
  Last Level III BMB:  0x00000000
     Map Header:: next  0x00000000  #extents: 28   obj#: 16840  flag: 0x10000000
  Inc # 0
  Extent Map
  -----------------------------------------------------------------
   0x01400768  length: 8    
   0x01402f48  length: 8    
   0x01402f50  length: 8    
   0x01402f58  length: 8    
   0x01402f60  length: 8    
   0x01402f68  length: 8    
   0x01402f70  length: 8    
   0x01402f78  length: 8    
   0x01402e80  length: 8    
   0x01402e88  length: 8    
   0x01402e90  length: 8    
   0x01402e98  length: 8    
   0x01402ea0  length: 8    
   0x01402ea8  length: 8    
   0x01402eb0  length: 8    
   0x01402eb8  length: 8    
   0x01403f80  length: 128  
   0x01404000  length: 128  
   0x01404080  length: 128  
   0x01404180  length: 128  
   0x01405800  length: 128  
   0x01405880  length: 128  
   0x01405900  length: 128  
   0x01405980  length: 128  
   0x01405a00  length: 128  
   0x01405a80  length: 128  
   0x01405b00  length: 128  
   0x01405b80  length: 128  
  
  Auxillary Map
  --------------------------------------------------------
   Extent 0     :  L1 dba:  0x01400768 Data dba:  0x0140076b
   Extent 1     :  L1 dba:  0x01400768 Data dba:  0x01402f48
   Extent 2     :  L1 dba:  0x01402f50 Data dba:  0x01402f51
   Extent 3     :  L1 dba:  0x01402f50 Data dba:  0x01402f58
   Extent 4     :  L1 dba:  0x01402f60 Data dba:  0x01402f61
   Extent 5     :  L1 dba:  0x01402f60 Data dba:  0x01402f68
   Extent 6     :  L1 dba:  0x01402f70 Data dba:  0x01402f71
   Extent 7     :  L1 dba:  0x01402f70 Data dba:  0x01402f78
   Extent 8     :  L1 dba:  0x01402e80 Data dba:  0x01402e81
   Extent 9     :  L1 dba:  0x01402e80 Data dba:  0x01402e88
   Extent 10    :  L1 dba:  0x01402e90 Data dba:  0x01402e91
   Extent 11    :  L1 dba:  0x01402e90 Data dba:  0x01402e98
   Extent 12    :  L1 dba:  0x01402ea0 Data dba:  0x01402ea1
   Extent 13    :  L1 dba:  0x01402ea0 Data dba:  0x01402ea8
   Extent 14    :  L1 dba:  0x01402eb0 Data dba:  0x01402eb1
   Extent 15    :  L1 dba:  0x01402eb0 Data dba:  0x01402eb8
   Extent 16    :  L1 dba:  0x01403f80 Data dba:  0x01403f82
   Extent 17    :  L1 dba:  0x01404000 Data dba:  0x01404002
   Extent 18    :  L1 dba:  0x01404080 Data dba:  0x01404082
   Extent 19    :  L1 dba:  0x01404180 Data dba:  0x01404182
   Extent 20    :  L1 dba:  0x01405800 Data dba:  0x01405802
   Extent 21    :  L1 dba:  0x01405880 Data dba:  0x01405882
   Extent 22    :  L1 dba:  0x01405900 Data dba:  0x01405902
   Extent 23    :  L1 dba:  0x01405980 Data dba:  0x01405982
   Extent 24    :  L1 dba:  0x01405a00 Data dba:  0x01405a02
   Extent 25    :  L1 dba:  0x01405a80 Data dba:  0x01405a82
   Extent 26    :  L1 dba:  0x01405b00 Data dba:  0x01405b02
   Extent 27    :  L1 dba:  0x01405b80 Data dba:  0x01405b82
  --------------------------------------------------------
  
   Second Level Bitmap block DBAs
   --------------------------------------------------------
   DBA 1:   0x01400769

下面是我认为比较重要的segment header每个offset对应的含义：

offset desc
36 total extents
40 total blocks
48 HWM所在的ext#
52 HWM所在的ext#的第几个block(从0开始)
56 HWM所在的ext#的ext blocks
60 HWM所在的dba地址
76 HWM下有多少个block
92 LHWM所在的ext#
96 LHWM所在的ext#的第几个block(从0开始)
100 LHWM所在的ext#的ext size
104 LHWM所在的dba地址
120 LHWM下有多少个block
124 Level 1 BMB for High HWM block
128 Level 1 BMB for Low HWM block
213 block size
220 L2 Array start offset
224 First Level 3 BMB
228 L2 Hint for inserts
236 Last Level 1 BMB
240 Last Level II BMB
244 Last Level III BMB
264 Map Header的extents
272 Map Header的obj#
276 Map Header的flag
280 ext#为0的block_id
284 ext#为0的extent blocks
288 ext#为1的block_id
292 ext#为1的extent blocks
……以此类推循环
2736 aux map信息，ext#为0的L1 dba
2740 aux map信息，ext#为0的data dba
2744 aux map信息，ext#为1的L1 dba
2748 aux map信息，ext#为1的data dba
……以此类推循环
5192 Second Level Bitmap block DBAs

确认了需要恢复的内容之后，还需要确认是否有对象占用了truncate释放的空间，依据是用从redo dump找到的truncate前的extent map和dba_extents对比。如果有对象占用需要先move对象到其他表空间。如何从redo dump找到extent map见后面段头块的extent map恢复。

无覆盖的TRUNCATE恢复

重要：假如确实失误truncate了表，需要马上停应用，最好将表空间设置为offline或者read only，避免数据被覆盖。

通过之前对table full scan、segment header和前面truncate原理的分析，tfs不会读取L1、L2块，所以恢复的时候L1、L2块和具体存放数据的块都不用管，只需尝试通过修改段头块和基表信息来恢复truncate的数据，bbed修改段头块的具体offset含义见segment header章节。

1.修改段头块dataobj#(由于表可能不止一次被truncate，所以获取之前dataobj#最好的办法是通过logminer或者redo dump，这里我使用的redo dump)

REDO RECORD - Thread:1 RBA: 0x000055.0000001b.0080 LEN: 0x00ac VLD: 0x01
SCN: 0x0000.003ed056 SUBSCN:  1 04/21/2018 12:25:34
CHANGE #1 TYP:0 CLS:34 AFN:6 DBA:0x018002ee OBJ:4294967295 SCN:0x0000.003ed054 SEQ:1 OP:5.1 ENC:0 RBL:0
ktudb redo: siz: 64 spc: 822 flg: 0x0022 seq: 0x017b rec: 0x33
            xid:  0x0009.00f.00000353  
ktubu redo: slt: 15 rci: 50 opc: 14.5 objn: 1 objd: 16840 tsn: 5
Undo type:  Regular undo       Undo type:  Last buffer split:  No
Tablespace Undo:  Yes
             0x00000000
kteopu undo - undo operation on extent map
       segdba: 0x140076a  class: 4  mapdba:0x140076a  offset: 2
rbr extent - dba: 0x0  nbk: 0x0
kteop redo - redo operation on extent map
   CDOBJ: new object number:16840
CHANGE #2 TYP:0 CLS:4 AFN:5 DBA:0x0140076a OBJ:16840 SCN:0x0000.003ed050 SEQ:2 OP:14.4 ENC:0 RBL:0
kteop redo - redo operation on extent map
   CDOBJ: new object number:16860

从redo dump信息可以看到段头块0x0140076a的dataobj#从16840变成了16860，所以这里需要将段头块的dataobj#改回16840。

BBED> set file 4 block 1898
        FILE#           4
        BLOCK#          1898
 
BBED> d offset 272 count 8
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 1898             Offsets:  272 to  279           Dba:0x0100076a
------------------------------------------------------------------------
dc410000 00000010
 
<32 bytes per line>
 
BBED> m /x c841 offset 272
Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 1898             Offsets:  272 to  279           Dba:0x0100076a
------------------------------------------------------------------------
c8410000 00000010
 
<32 bytes per line>
 
BBED> sum apply
Check value for File 4, Block 1898:
current = 0xe90e, required = 0xe90e

仅仅修改段头块的dataobj#再次查询表会报ORA-08103: object no longer exists，原因是基表没有修改。查询的时候会通过表名去找到该表的dataobj#。

SYS@TEST(test):1>select count(*) from test.truncate_table;
select count(*) from test.truncate_table
                          *
ERROR at line 1:
ORA-08103: object no longer exists
 
SYS@TEST(test):1>UPDATE OBJ$ SET DATAOBJ#=16840 WHERE OBJ#=16840;
 
1 row updated.
 
SYS@TEST(test):1>UPDATE TAB$ SET DATAOBJ#=16840 WHERE OBJ#=16840;
 
1 row updated.
 
SYS@TEST(test):1>COMMIT;
 
Commit complete.
 
SYS@TEST(test):1>alter system flush buffer_cache;
 
System altered.
 
SYS@TEST(test):1>alter system flush shared_pool;
 
System altered.
 
SYS@TEST(test):1>select count(*) from test.truncate_table;
 
  COUNT(*)
----------
         0

2.恢复段头块HWM（HWM信息可以从redo dump中获取）

REDO RECORD - Thread:1 RBA: 0x000055.00000016.0148 LEN: 0x01b8 VLD: 0x01
SCN: 0x0000.003ed050 SUBSCN:  5 04/21/2018 12:25:34
CHANGE #1 TYP:0 CLS:34 AFN:6 DBA:0x018002ee OBJ:4294967295 SCN:0x0000.003ed050 SEQ:3 OP:5.1 ENC:0 RBL:0
ktudb redo: siz: 164 spc: 1112 flg: 0x0022 seq: 0x017b rec: 0x30
            xid:  0x0009.00f.00000353  
ktubu redo: slt: 15 rci: 47 opc: 13.29 objn: 16840 objd: 16840 tsn: 5
Undo type:  Regular undo       Undo type:  Last buffer split:  No
Tablespace Undo:  No
             0x00000000
Segment Header Undo
Seghdr dba:  0x0140076a Mapblock dba:  0x00000000 Mapredo Offset: 4 scls: 4 mcls: 140733193388039
Both the HWMs
Low HWM
      Highwater::  0x01405b83  ext#: 27     blk#: 3      ext size: 128  
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 1539  
  mapblk  0x00000000  offset: 27    
lfdba:  0x01405b80
High HWM
      Highwater::  0x01405b83  ext#: 27     blk#: 3      ext size: 128  
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 1539  
  mapblk  0x00000000  offset: 27    
lfdba:  0x01405b80 hint dba:  0x01400769
Lasts in Header
LF: 20994945 LS: 20973417 LT: 0 FT: 0
CHANGE #2 TYP:0 CLS:4 AFN:5 DBA:0x0140076a OBJ:16840 SCN:0x0000.003ed050 SEQ:1 OP:13.28 ENC:0 RBL:0Both the HWMs
Low HWM
      Highwater::  0x0140076b  ext#: 0      blk#: 3      ext size: 8    
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 0    
  mapblk  0x00000000  offset: 0    
lfdba:  0x01400768
High HWM
      Highwater::  0x0140076b  ext#: 0      blk#: 3      ext size: 8    
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 0    
  mapblk  0x00000000  offset: 0    
lfdba:  0x01400768 hint dba:  0x01400769
Lasts in Header
LF: 20973416 LS: 20973417 LT: 0 FT: 0
CHANGE #3 TYP:0 CLS:8 AFN:5 DBA:0x01400768 OBJ:16840 SCN:0x0000.003ed050 SEQ:2 OP:13.22 ENC:0 RBL:0
Redo on Level1 Bitmap Block
Redo to set hwm
Opcode: 32      Highwater::  0x0140076b  ext#: 0      blk#: 3      ext size: 8    
  #blocks in seg. hdr's freelists: 0    
  #blocks below: 0    
  mapblk  0x00000000  offset: 0    

可以看到段头块0x0140076a的LHWM信息和HHWM是一样的，都是

Highwater:: 0x01405b83 ext#: 27 blk#: 3 ext size: 128
Highwater:: 0x0140076b ext#: 0 blk#: 3 ext size: 8

所以这里恢HWM信息只需要根据redo dump改回去即可。

m /x 1b offset 48
m /x 1b offset 92
m /x 03 offset 52
m /x 03 offset 96
m /x 80 offset 56
m /x 80 offset 100
m /x 835b offset 60
m /x 4001 offset 62
m /x 835b offset 104
m /x 4001 offset 106

3.恢复段头块extent map，Auxillary Map以及extent个数(extent信息和aux map信息同样可以从redo dump中获取)

REDO RECORD - Thread:1 RBA: 0x000055.00000027.0180 LEN: 0x0138 VLD: 0x01
SCN: 0x0000.003ed061 SUBSCN:  3 04/21/2018 12:25:35
CHANGE #1 TYP:0 CLS:17 AFN:6 DBA:0x01800120 OBJ:4294967295 SCN:0x0000.003ed061 SEQ:1 OP:5.2 ENC:0 RBL:0
ktudh redo: slt: 0x0014 sqn: 0x00000000 flg: 0x0002 siz: 112 fbi: 248
            uba: 0x018006ea.018c.1f    pxid:  0x0000.000.00000000
CHANGE #2 TYP:0 CLS:18 AFN:6 DBA:0x018006ea OBJ:4294967295 SCN:0x0000.003ed061 SEQ:1 OP:5.1 ENC:0 RBL:0
ktudb redo: siz: 112 spc: 3358 flg: 0x0022 seq: 0x018c rec: 0x1f
            xid:  0x0001.014.00000297  
ktubu redo: slt: 20 rci: 0 opc: 14.5 objn: 1 objd: 16860 tsn: 5
Undo type:  Regular undo       Undo type:  Last buffer split:  No
Tablespace Undo:  Yes
             0x00000000
kteopu undo - undo operation on extent map
       segdba: 0x140076a  class: 4  mapdba:0x140076a  offset: 3
rbr extent - dba: 0x0  nbk: 0x0
kteop redo - redo operation on extent map
   ADD: dba:0x1405b80 len:128 at offset:27 --truncate前的extent信息
  ADDAXT: offset:27 fdba:x01405b80 bdba:0x01405b82 --truncate前的aux map信息
   SETSTAT: exts:28 blks:1664 lastmap:0x0 mapcnt:0
CHANGE #3 TYP:0 CLS:4 AFN:5 DBA:0x0140076a OBJ:16860 SCN:0x0000.003ed061 SEQ:2 OP:14.4 ENC:0 RBL:0
kteop redo - redo operation on extent map
   DELETE: entry:27
   shift back: dba:0x0 len:0
   SETSTAT: exts:27 blks:1536 lastmap:0x0 mapcnt:0

从redo dump可以发现truncate操作对于extent map和aux map是从最后一个extent开始逐一删除的，这里可以看到该表的extent总共有28个，ext#为27是该表最后一个extent，block_id为0x1405b80，该extent size为128个块，以此类推很容易可以通过简单的grep找出extent map；同理ext#为27的aux map的L1 dba为x01405b80，data dba为0x01405b82，以此类推很容易可以通过简单的grep找出aux map。

extent map:
[root@prim1-11g ~]# grep -i "ADD: dba" /u01/app/oracle/diag/rdbms/test/test/trace/test_ora_7611.trc
   ADD: dba:0x1405b80 len:128 at offset:27
   ADD: dba:0x1405b00 len:128 at offset:26
   ADD: dba:0x1405a80 len:128 at offset:25
   ADD: dba:0x1405a00 len:128 at offset:24
   ADD: dba:0x1405980 len:128 at offset:23
   ADD: dba:0x1405900 len:128 at offset:22
   ADD: dba:0x1405880 len:128 at offset:21
   ADD: dba:0x1405800 len:128 at offset:20
   ADD: dba:0x1404180 len:128 at offset:19
   ADD: dba:0x1404080 len:128 at offset:18
   ADD: dba:0x1404000 len:128 at offset:17
   ADD: dba:0x1403f80 len:128 at offset:16
   ADD: dba:0x1402eb8 len:8 at offset:15
   ADD: dba:0x1402eb0 len:8 at offset:14
   ADD: dba:0x1402ea8 len:8 at offset:13
   ADD: dba:0x1402ea0 len:8 at offset:12
   ADD: dba:0x1402e98 len:8 at offset:11
   ADD: dba:0x1402e90 len:8 at offset:10
   ADD: dba:0x1402e88 len:8 at offset:9
   ADD: dba:0x1402e80 len:8 at offset:8
   ADD: dba:0x1402f78 len:8 at offset:7
   ADD: dba:0x1402f70 len:8 at offset:6
   ADD: dba:0x1402f68 len:8 at offset:5
   ADD: dba:0x1402f60 len:8 at offset:4
   ADD: dba:0x1402f58 len:8 at offset:3
   ADD: dba:0x1402f50 len:8 at offset:2
   ADD: dba:0x1402f48 len:8 at offset:1
 
aux map:
[root@prim1-11g ~]# grep -i "ADDAXT:" /u01/app/oracle/diag/rdbms/test/test/trace/test_ora_7611.trc
  ADDAXT: offset:27 fdba:x01405b80 bdba:0x01405b82
  ADDAXT: offset:26 fdba:x01405b00 bdba:0x01405b02
  ADDAXT: offset:25 fdba:x01405a80 bdba:0x01405a82
  ADDAXT: offset:24 fdba:x01405a00 bdba:0x01405a02
  ADDAXT: offset:23 fdba:x01405980 bdba:0x01405982
  ADDAXT: offset:22 fdba:x01405900 bdba:0x01405902
  ADDAXT: offset:21 fdba:x01405880 bdba:0x01405882
  ADDAXT: offset:20 fdba:x01405800 bdba:0x01405802
  ADDAXT: offset:19 fdba:x01404180 bdba:0x01404182
  ADDAXT: offset:18 fdba:x01404080 bdba:0x01404082
  ADDAXT: offset:17 fdba:x01404000 bdba:0x01404002
  ADDAXT: offset:16 fdba:x01403f80 bdba:0x01403f82
  ADDAXT: offset:15 fdba:x01402eb0 bdba:0x01402eb8
  ADDAXT: offset:14 fdba:x01402eb0 bdba:0x01402eb1
  ADDAXT: offset:13 fdba:x01402ea0 bdba:0x01402ea8
  ADDAXT: offset:12 fdba:x01402ea0 bdba:0x01402ea1
  ADDAXT: offset:11 fdba:x01402e90 bdba:0x01402e98
  ADDAXT: offset:10 fdba:x01402e90 bdba:0x01402e91
  ADDAXT: offset:9 fdba:x01402e80 bdba:0x01402e88
  ADDAXT: offset:8 fdba:x01402e80 bdba:0x01402e81
  ADDAXT: offset:7 fdba:x01402f70 bdba:0x01402f78
  ADDAXT: offset:6 fdba:x01402f70 bdba:0x01402f71
  ADDAXT: offset:5 fdba:x01402f60 bdba:0x01402f68
  ADDAXT: offset:4 fdba:x01402f60 bdba:0x01402f61
  ADDAXT: offset:3 fdba:x01402f50 bdba:0x01402f58
  ADDAXT: offset:2 fdba:x01402f50 bdba:0x01402f51
 ADDAXT: offset:1 fdba:x01400768 bdba:0x01402f48

这里可以写脚本根据segment header章节offset的含义来生成bbed命令，由于bbed命令较长省略一部分。

修改exts信息：
m /x 1c offset 36
m /x 1c offset 264
将grep出的数据作为一整列全部导入表中用sql生成bbed命令
如创建表：create table aux_map(a varchar2(2000);create table ext_map(a varchar2(2000);插入数据后就可以用下列sql生成命令
生成aux map的bbed命令
with aa as (
select replace(regexp_substr(a,'[^:]+',1,3),'fdba','') ext#,
(replace(regexp_substr(a,'[^:]+',1,3),'fdba','')-1)*8+2744 offset,
trim(replace(regexp_substr(a,'[^:]+',1,4),'bdba','')) l1,
trim(regexp_substr(a,'[^:]+',1,5)) data
from aux_map)
select 'm /x '||a||' offset '||offset||chr(10)||'m /x '||b||' offset '||to_char(offset+2)||chr(10)||'m /x '||c||' offset '||to_char(offset+4)||chr(10)||'m /x '||d||' offset '||to_char(offset+6) from
(select ext#,to_number(offset) offset,substr(l1,-2,2)||substr(l1,-4,2) a,substr(l1,-6,2)||substr(l1,-8,2) b,substr(data,-2,2)||substr(data,-4,2) c,substr(data,-6,2)||substr(data,-8,2) d
from aa)
 
生成ext map的bbed命令
with aa as (
select trim(replace(replace(regexp_substr(a,'[^:]+',1,3),'len',''),'x','x0')) block_id,
(regexp_substr(a,'[^:]+',1,5)-1)*8+288 offset,
lpad(trim((to_char((replace(regexp_substr(a,'[^:]+',1,4),'at offset','')),'xxxx'))),2,0) blocks,
regexp_substr(a,'[^:]+',1,5) ext#
from ext_map)
select 'm /x '||a||' offset '||offset||chr(10)||'m /x '||b||' offset '||to_char(offset+2)||chr(10)||'m /x '||blocks||' offset '||to_char(offset+4) from
(select ext#,to_number(offset) offset,substr(block_id,-2,2)||substr(block_id,-4,2) a,substr(block_id,-6,2)||substr(block_id,-8,2) b,blocks
from aa)
 
bbed修改后extent map恢复成功：
BBED> d /v offset 280
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 1898    Offsets:  280 to  579  Dba:0x0100076a
-------------------------------------------------------
68074001 08000000 482f4001 08000000 l h.@.....H/@.....
502f4001 08000000 582f4001 08000000 l P/@.....X/@.....
602f4001 08000000 682f4001 08000000 l `/@.....h/@.....
702f4001 08000000 782f4001 08000000 l p/@.....x/@.....
802e4001 08000000 882e4001 08000000 l ..@.......@.....
902e4001 08000000 982e4001 08000000 l ..@.......@.....
a02e4001 08000000 a82e4001 08000000 l ..@.......@.....
b02e4001 08000000 b82e4001 08000000 l ..@.......@.....
803f4001 80000000 00404001 80000000 l .?@......@@.....
80404001 80000000 80414001 80000000 l .@@......A@.....
00584001 80000000 80584001 80000000 l .X@......X@.....
00594001 80000000 80594001 80000000 l .Y@......Y@.....
005a4001 80000000 805a4001 80000000 l .Z@......Z@.....
005b4001 80000000 805b4001 80000000 l .[@......[@.....
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000          l ............
 
<16 bytes per line>
 
aux map恢复成功：
BBED> d /v offset 2736
File: /u01/app/oracle/oradata/test/users01.dbf (4)
Block: 1898    Offsets: 2736 to 3035  Dba:0x0100076a
-------------------------------------------------------
68074001 6b074001 68074001 482f4001 l h.@.k.@.h.@.H/@.
502f4001 512f4001 502f4001 582f4001 l P/@.Q/@.P/@.X/@.
602f4001 612f4001 602f4001 682f4001 l `/@.a/@.`/@.h/@.
702f4001 712f4001 702f4001 782f4001 l p/@.q/@.p/@.x/@.
802e4001 812e4001 802e4001 882e4001 l ..@...@...@...@.
902e4001 912e4001 902e4001 982e4001 l ..@...@...@...@.
a02e4001 a12e4001 a02e4001 a82e4001 l ..@...@...@...@.
b02e4001 b12e4001 b02e4001 b82e4001 l ..@...@...@...@.
803f4001 823f4001 00404001 02404001 l .?@..?@..@@..@@.
80404001 82404001 80414001 82414001 l .@@..@@..A@..A@.
00584001 02584001 80584001 82584001 l .X@..X@..X@..X@.
00594001 02594001 80594001 82594001 l .Y@..Y@..Y@..Y@.
005a4001 025a4001 805a4001 825a4001 l .Z@..Z@..Z@..Z@.
005b4001 025b4001 805b4001 825b4001 l .[@..[@..[@..[@.
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000 00000000 l ................
00000000 00000000 00000000          l ............
 
<16 bytes per line>

最后恢复成功，这里由于L1、L2没有恢复，所以insert会有问题，但是可以通过CTAS重建表完全恢复。

SYS@TEST(test):1>select count(*) from test.truncate_table;
 
  COUNT(*)
----------
    113426
 
SYS@TEST(test):1>insert into test.truncate_table select * from dba_objects;
insert into test.truncate_table select * from dba_objects
                 *
ERROR at line 1:
ORA-00600: internal error code, arguments: [ktspgfblk3:kcbz_objdchk], [0], [0], [1], [], [], [], [], [], [], [], []
 
 
SYS@TEST(test):1>CREATE TABLE TEST.RECOVER_TABLE AS SELECT * FROM TEST.TRUNCATE_TABLE;
 
Table created.
 
SYS@TEST(test):1>INSERT INTO TEST.RECOVER_TABLE select * from dba_objects WHERE ROWNUM=1;
 
1 row created.
 
SYS@TEST(test):1>COMMIT;
 
Commit complete.

最后恢复成功。

关于作者

李翔宇，云和恩墨西区交付技术顾问，长期服务移动运营商行业客户，熟悉Oracle性能优化，故障诊断，特殊恢复。

今年的数据技术嘉年华大会上，李翔宇老师将带来题为《在通过案例深入解析Oracle内部原理》的演讲，与大家一起探索CBO和ASM rebalance的一些内部机制，精彩不容错过！